U.S. Pat. No. 4,446,393 corresponding to Japanese Examined Patent Publication (kokoku) No. H04-049336 and Japanese Unexamined Patent Publication No. 2006-271121 disclose conventional field coils each formed by winding edgewise a rectangular wire strap.
An example of methods of manufacturing a pair of first and second field coil members to be used for producing a field coil assembly, which is disclosed in the US patent publication and/or JP Unexamined Patent Publications will be described hereinafter with reference to FIGS. 18A to 18F and 19A to 19F.
As illustrated in FIG. 18A, in order to produce the first field coil member, one continuous rectangular wire strap 100 with a predetermined length suitable to produce one filed coil member and a pair of first and second coil forms 110a and 110b are prepared.
Each of the first and second coil forms 110a and 110b has a round rectangular cylindrical shape. The rectangular wire strap 100 has a thickness substantially less than the width of its major sides 100a. 
One minor side of one end portion of the wire strap 100 is so contacted onto the periphery of the first coil form 110a as to leave a predetermined lengthened end Ta thereof. The one minor side of the one end portion of the wire strap 100 is clamped by a clamp mechanism of the first coil form 110a. 
Similarly, the other minor side of the other end of the wire strap 100 is so contacted onto the periphery of the second coil form 110b as to leave a predetermined lengthened end Tb thereof. The other minor side of the other end portion of the wire strap 100 is clamped by a clamp mechanism of the second coil form 110b. 
Next, as illustrated in FIG. 18B, the first and second coil forms 110a and 110b are respectively rotated on their center axes at 180 degrees in a predetermined direction, such as counter-clockwise direction in FIG. 18B, while they come close to each other under the wire strap 100 being subjected to a tension.
This allows the one and the other end portions of the wire strap 100 to be wound edgewise on the peripheries of the first and second coil forms 110a and 110b. 
Next, as illustrated in FIG. 18C, the first and second coil forms 110a and 110b are respectively rotated on their center axes at 90 degrees in the counter-clockwise direction such that each of the start ends Ta and Tb of the wire strap 100 crosses over one of the major sides 100a of the wire strap 100. This forms a first convolution (first layer) wound edgewise around a corresponding one of the peripheries of the first and second coil forms 110a and 110b. 
Thereafter, a predetermined number of rotations of the coil forms 110a and 110b in the counter-clockwise direction are carried out.
Specifically, execution of the predetermined number of rotations of the coil forms 110a and 110b allows the wire strap 100 to be wound at their minor sides (at their edges) on the outer peripheries of the first and second coil forms 110a and 110b from the one and the other ends of the wire strap 100 toward the center thereof.
This forms successive convolutions of the wire strap 100 wound edgewise around the first and second coil forms 110a and 110b, respectively. The successive loops proceed from the remaining center of the wire strap 100 away therefrom along the axial directions of the first and second coil forms 110a and 110b (see FIGS. 18D and 28E).
After completion of the predetermined number of rotations of the coil forms 110a and 110b, a pair of spaced-apart coil elements coupled to each other with a link portion 120 is generated (see FIG. 18E).
The pair of coil elements is folded at the link portion 120 such that the spaced-apart coil elements approach each other and that the start ends Ta and Tb of the wire strap 100 are substantially parallel to each other (see FIG. 18F). Removal of the pair of coil elements from the first and second coil forms 110a and 110b provides a first field coil member 130 consisting of a pair of series-connected edgewise coils 130a and 130b. 
The start end Ta of the series-connected edgewise coil 130a serves as a coil end thereof extending outwardly from one portion of the first convolution of the coil 130a in a direction orthogonal to the axial direction thereof. Similarly, the start end Tb of the series-connected edgewise coil 130b serves as a coil end thereof extending outwardly from a corresponding portion of the first convolution of the coil 130b in a direction orthogonal to the axial direction thereof.
In addition, as illustrated in FIG. 19A, in order to produce the second field coil member, the identical wire strap 100 and the identical first and second cylindrical coil forms 110a and 110b are prepared.
In the first different point of producing the second field coil member from the first field coil member, the other minor side of the one end portion of the wire strap 100 is so contacted onto the periphery of the first coil form 110a as to leave a start end Ta thereof. The other minor side of the one end portion of the wire strap 100 is clamped by the clamp mechanism of the first coil form 110a. 
In addition, the one minor side of the other end of the wire strap 100 is so contacted onto the periphery of the second coil form 110b as to leave a start end Tb thereof. The one minor side of the other end portion of the wire strap 100 is clamped by the clamp mechanism of the second coil form 110b. 
Next, in the second different point, as illustrated in FIG. 19B, the first and second coil forms 110a and 110b are respectively rotated on their center axes at 180 degrees in a predetermined direction opposite to the counter-clockwise direction, such as clockwise direction in FIG. 19B, while they come close to each other under the wire strap 100 being subjected to a tension.
In this way, like the first field coil member, the identical predetermined number of rotations of the coil forms 110a and 110b in the clockwise direction are carried out.
Specifically, execution of the identical predetermined number of rotations of the coil forms 110a and 110b allows the wire strap 100 to be wound at their minor sides (at their edges) on the outer peripheries of the first and second coil forms 110a and 110b from the one and the other ends of the wire strap 100 toward the center thereof.
This forms successive convolutions of the wire strap 100 wound edgewise around the first and second coil forms 110a and 110b, respectively. The successive loops proceed from the remaining center of the wire strap 100 away therefrom along the axial directions of the first and second coil forms 110a and 110b (see FIGS. 19C to 19E).
After completion of the predetermined number of rotations of the coil forms 110a and 110b, a pair of spaced-apart coil elements coupled to each other with a link portion 120 is generated (see FIG. 19E).
The pair of coil elements is folded at the link portion 120 such that the spaced-apart coil elements approach each other and that the start ends Ta and Tb of the wire strap 100 are substantially parallel to each other (see FIG. 19F).
Removal of the pair of coil elements from the first and second coil forms 110a and 110b provides a second field coil member 140 consisting of a pair of series-connected edgewise coils 140a and 140b. 
The start end Ta of the series-connected edgewise coil 140a serves as a coil end thereof extending outwardly from one portion of the first convolution of the coil 140a in a direction orthogonal to the axial direction thereof. Similarly, the start end Tb of the series-connected edgewise coil 130b serves as a coil end thereof extending outwardly from a corresponding portion of the first convolution of the coil 130b in a direction orthogonal to the axial direction thereof.
As illustrated in FIGS. 18F and 19F, assuming that the first field coil member 130 and the second field coil member 140 are arranged across a line such that the coil 130a and the coil 140b are opposite to each other, the first field coil member 130 and the second field coil member 140 are symmetrical with respect to the line.